Description
ABSTRACT
The main aim of any electric power supply in the world is to provide uninterrupted power supply at all times to all its consumers. Although in developing countries, the electric power generated to meet the demands of the growing consumers of electricity is insufficient hence instability and outage.
Power instability or outage in general does not promote development in the public and private sector. The inventors do not feel secure to come into a country with constant or frequent power failure.
These limit the development of industries. In addition, there are processes that cannot be interrupted because of their importance. For instance, surgery operation in hospitals, transfer of money between bank and lots more. Power instability and outage in developing countries (Nigeria) creates a need for alternative source of power to backup the main supply.
Automatic changeover switches find a wide application scope wherever the reliability of electric supply from the utilities is low and it is used in lighting motor circuits wherever continuity of supply is necessary. For switching to an alternative source from main supply and vice versa.
This project is a design of an automatic changeover switch this means that when there is any mains failure, the automatic changeover switch will change to an alternative power supply (GENERATOR) and back to the main supply when it is restored.
The purpose of this project is to maintain constant supply to the main circuit that is being supplied by making up for the time delay that usually accompanies the manual switching from one source to another.
The design comprises of the power connection circuit and control connection circuit. The main components to be used include contactor, relay, timers, rectifiere.t.c.
TABLE OF CONTENTS
Title Page i
Certification ii
Acknowledgements iii
Abstract iv
Table of Contents v
CHAPTER ONE
1.1 Introduction 1
1.2 Aim and Objective of the Project 3
1.3 Scope of the Project 3
CHAPTER TWO
2.1 Literature Review 5
2.2 Manual Change-over Switch 5
2.3 Automatic Change-over Switch 6
2.4 Related Work 10
2.5 Reasons for Automatic Change-over Switch 16
2.6 Problems of Automatic Change-over Switch 17
CHAPTER THREE
3.1 Methodology (Material and Methods) 18
3.2 Circuit Conductor 18
3.3 Circuit Breaker 19
3.4 Reset Timer 20
3.5 Contactor 21
3.6 Operation of Timer Delay 24
3.7 Principle of Operation 25
CHAPTER FOUR
4.0 Construction 29
4.1 List of Component Used 29
4.2 Vero Board 29
4.3 Bread Board 30
4.4 Soldering Iron 33
4.5.1 Testing, Maintenance and Discussion 36
4.5.2 Polarity Test 36
4.5.3 Insulation Resistance Test between the Live and Neutral Conductors 37
4.5.4 Earthling Test 37
4.6 Maintenance of Contactor and Installation 37
CHAPTER FIVE
5.1 Conclusion 39
5.2 Recommendation 39
References 40
Bill of Engineering Measurement and Evaluation (BEME) 41
CHAPTER ONE
1.1 INTRODUCTION
Power instability in developing countries creates a need for automation of electrical power generation or alternative sources of power to back-up the utility supply. This automation is requiring as the rate of power outages become predominantly high. Research in the field of electrical electronics engineering has led to the tremendous discovers and inventions especially in the area of automation and power control. These invention have been useful in solving the over-in.
Creating problem posed by power generation, distribution and control, which has been a cause of concern especially in the third world countries (developing countries) like Nigeria. Most industrial and commercial process is dependents on electric power and if process of a change-over is manual, serious time is not only wasted but it creates room for human error (in the area of change over connections) which could result in great economic loss.
This project is all about the construction of an automatic generator change-over panel with timer which aids in the switching over to alternation power supply authority i.e.Power Holding Company of Nigeria (PHCN) popularly known as NEPA which is the main power regulating body in Nigeria. This project consist of circuit breakers, electromagnetic contactor which carry heavy load current relay which work with the principle of electromagnetic induction because it will receive electrical signal to trigger and neumatic timer all incorporated and interconnected to achieve the desire goal.
Also this project is constructed in such a way that provision is made for manually operation (it can be operated manually) when necessary for required for example, in the situation whereby voltage supplied by the authority (PHCN) is fluctuating and one may decided not to use it, so the constructed automatic change-over panel can be permanently switch to generator set temporarily pending the time that utility supply is stable moreover in the hospital where where surgery operations is needed to be carry out and power outage for even five second cause damages, one may decide to neglect the supply from authority (PHCN) and permanently switch the panel to manual operation pending the time or period by which surgery operation is completed. During the pending period this change-over will be working continuously in manual operation. Fill someone or the operation has to switch over to automatic operation. As said earlier, provision is made for these types of generation in this project and there is separate switch that performed the function.
1.2 PROBLEM STATEMENT
Power failure or outage in a country, state or city is highly detrimental to development in public and private industries. The insecurity associated with constant or frequent power failure or outage brings about limitation to power consistent investments, thus hampering the development of industries and multinational ventures. Processes like carrying out surgical operations in hospitals, laboratories which require constant power supply for research, money transactions between banks and more require constant use of uninterrupted power. In other to solve this problem, an automatic changeover switch was invented. This research covers the design and construction of a single phase digital automatic power changeover. It has the capacity to automatically switch power from national grid to generator and vice versa, once there is power failure in any of the two power supplies and at the same time has the capacity of shutting down a generator set once the mains grid is been restored.
1.3 AIM AND OBJECTIVE OF THE PROJECT
The aim of the project is to design and construction automatic change-over switch load from the mains power supply (PHCN) to a backup power supply (Generator) with simplicity.
The advantages of this project cannot be over emphasized, since outage is a major problem is the advent developing nations like Nigeria, for example, power failure of minute in an airport terminal can create losses that could run into millions of dollars due to loss in air traffic system control the ability for back-up to start and change-over automatically becomes imperative under such circumstances.
Also, this project could play a large role in the security in banks and companies i.e. an outage of up to ten minute in an organized setup is enough to do all the damage required with such an automatic change-over device in place the generator backup would no longer have to depend on security men and of course reduced fear of system breakdown in the companies there by ensuring smooth running of economics activities.
1.4 SCOPE OF THE PROJECT
Basically, this project is a three phase automatic change-over device with the power capacity of 50KVA. Generator as deducted from my calculations it shows that generator of power rating ranging from 0.5KVA to 50KVA is required to be use for this project though the contacts of electromagnetic contactor relays and circuit breakers. Also the maximum load current should be between the ratings of 10A to 90A load current. Therefore the use of 10Amperes in this project is because of future extension.
1.5 PURPOSE OF THE PROJECT
The main purpose of this work is to provide a means of having uninterruptible power supply in our home, office, workshops or industries.
1.6 SIGNIFICANCE OF THE PROJECT
Industries require three phases power to run their machinery. Some of them require continuous \ uninterrupted power to maintain their data.
Auto three phase power changeover introduces an automatic solution to overcome power interruption by automatically switching power from national grid to generator and vice versa
This automatic change over unit operates in three phase system. The automatic change over switch has the following advantages;
It minimizes damages to lives/equipment since it has its own monitoring system and its switching requires no human contact with the switch, thus eliminating human error.
It reduces its change over timing to the minimum due to its fast response to power outage.
It maintains high quality of service through its fast and prompt response.
Moreover, the size and captivity of the unit will depend upon the load for which it will be used. The unit is also portable, easy, convenient and safe to install.
1.7 LIMITATION OF THE PROJECT
In the course of designing this project, different kinds of problem was notice such as:
Difficulty in troubleshooting with circuit without the circuit diagram
Difficulty in connecting the output without the three phases short-circuiting, until a multiplexing circuit was gotten.
Difficult in wiring because of the strong wiring the project required.
This automatic change over unit operates in three phase system.
1.8 APPLICATION OF THE PROJECT
This device is used in the following places:
home,
office,
worship places
workshops or industries
1.9 METHODOLOGY
To achieve the aim and objectives of this work, the following are the steps involved:
Study of the previous work on the project so as to improve it efficiency.
Draw a block diagram.
Test for continuity of components and devices,
Design and calculation for the changeover was carried out.
Studying of various component used in circuit.
Construct a digital changeover circuit.
Finally, the whole device was cased and final test was carried out.
1.9 DEFINITION OF TERMS
POWER OUTAGE / POWER FAILURE: A power outage is the loss of the electrical power network supply to an end user.
AUTOMATIC CHANGEOVER is device that automatically transfers power from generator supply to PHCN supply when available and stops the generator without human intervention
1.10 PROJECT ORGANIZATION
The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.
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